Display Device and Manufacturing Method Thereof

ABSTRACT

Conventionally, photolithography and anisotropic etching are performed to form a plug between an electrode and a wiring, etc., thereby increasing the number of steps, getting the throughput worse, and producing unnecessary materials. To solve the problems, the present invention provides a method for manufacturing a display device, including the formation steps of a conductive layer or wirings, and a contact plug that can treat a larger substrate. In the case of forming a plug for electrically connecting conductive patterns comprising plural layers, a pillar made of a conductor is formed over a base conductive layer pattern, and then, after an insulating film is formed over the entire surface, the insulating film is etched back to expose the conductor pillar, and a conductive pattern in an upper layer is formed by ink jetting. In this case, when the conductor pillar is processed, a resist to be a mask can be formed in itself by ink jetting.

This application is based on Japanese Patent Application serial no.2003-086392 filed in Japan Patent Office on 26, Mar. 2003, the contentsof which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a displaydevice. Specifically, the present invention relates to a method formanufacturing a display device including a wiring formation step by anink jetting method and a contact plug formation step to electricallyconnect the wirings.

2. Description of the Related Art

A thin film transistor (TFT) formed by using a thin film on aninsulating surface is widely applied to integrated circuits and thelike, in many cases, is used as a switching element. Application of adisplay panel using TFTs greatly expands, in particular, into alarge-scale display device. Thus, high definition, high aperture ratio,high-reliability, and growth in size for a screen are requiredextremely.

A method for manufacturing wirings in such a device using thin filmtransistors is as follows: after a contact hole to connect to aparticular region of a substrate is formed by a combination ofphotolithography and anisotropic etching, a film of a conductive layeris formed over the entire surface, and then, photolithography andanisotropic etching are preformed by using a mask. (Reference 1:Japanese Patent Laid-Open No. 2002-359246)

As in the above reference 1, in the case where contact holes connectingwith a base conductive layer are opened, a resist is patterned byphotolithography once, the contact holes are opened selectively byanisotropic etching, and an unnecessary resist is removed. Thereafter,in the case of forming wirings, a conductive layer is deposited over theentire surface, and a resist is patterned by photolithography again, andthen, the wirings are processed by anisotropic etching. Like this, twophotolithography steps are required for forming up the wirings from thecontact holes, and thus, the number of steps is increased. Further, inthe case of such a wiring etching treatment, for example, when an ICPetching apparatus is used, selective ratio of a resist and a conductivelayer vary and the length or width of the conductive layer varies in thesubstrate, according to etching conditions such as bias power density,ICP power density, pressure, total flow of etching gases, an oxygenationfactor and a temperature of a lower electrode. When an etching treatmentis performed, the throughput gets worse since a step of forming a maskis necessary. The conductive layer is formed over the entire surface,and then, an etching treatment is performed to provide the conductivelayer with a desired shape, therefore, an unnecessary material isproduced. Such a problem is serious in the case of forming wirings overa large size substrate of which side exceeds 1.0 m.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above describedproblems. It is an object of the present invention to provide a methodfor manufacturing a display device comprising multilayer wirings thatcan cope with a large size substrate, or a conductive layer and acontact plug connecting them electrically. Further, it is another objectof the present invention to provide a method for manufacturing a displaydevice, including the formation steps of a conductive layer or wirings,and a contact plug by which the throughput or usability of materials canbe enhanced.

The present invention takes measures that are described hereinafter inorder to solve the above described conventional problems.

In the case of forming a plug for electrically connecting a conductivepattern comprising a layer or a plurality of layers, with wirings or aconductive pattern formed in an upper layer, a pillar made of aconductor is formed over a base conductive layer pattern once, and then,after a layer or a plurality of layers of an insulating film is formedover the entire surface, the insulating film is etched back to exposethe conductor (conductive) pillar, and a conductive pattern is formed byink jetting (an ink jet method). In this case, when the conductor pillaris processed, it is possible to form a resist to be a mask in itself byink jetting. For the resist material, a material having selectivity indry etching processing can be used as well as a conventional organicresin. For example, an inorganic material such as SiO₂ or a metalmaterial, in particular, a noble metal such as Au, Ag, Cu, or Pt whichis hard to be etched by dry etching, or the like, can be also used forthe resist material. When a metal material is used for the resistmaterial in etching, there is an advantage that the metal material isnot required to be removed after processing.

In other words, patterning is performed easily by jetting resist fromink heads, and a conductive layer is formed over an insulating surfaceby jetting composition including a conductive material. By combining thesteps, a conductive layer pattern for a contact plug, wirings, and thelike to connect with the contact plug etc., is fowled without performingphotolithography. The conductive layer may include a source wiring, adrain wiring, a pixel electrode, an opposite electrode and the like thathave conductivity. The conductive layer can be formed according to thepresent invention.

According to one aspect of the present invention, a layer or a pluralityof layers of a conductive layer is formed over a semiconductor formedover a substrate having an insulating surface, by ink jetting. A pillarthat is made of the same type conductor as the above conductor or adifferent type conductor is formed on a particular region of theconductive layer. The pillar made of the conductor can be formed by amethod in which a conductive layer is formed over the entire surfaceonce, and a resist pattern is formed on a desired local portion of theconductive layer, and then, anisotropic etching is performed thereon.Thereafter, after forming one layer or plural layers of an insulator is(are) over the entire surface, the conductor pillar is exposed byetching back the insulating film. Lastly, wirings for electricallyconnecting to the conductor pillar, a pixel electrode, or conductivepatterns of a light emitting layer, an opposite electrode, or the likeare formed by ink jetting.

In accordance with one aspect of the invention, the method ofmanufacturing a display device comprises steps of:

forming a first wiring over a substrate having an insulating surface;

forming a conductive film over the substrate so as to cover the firstwiring;

forming a resist pattern on the conductive film by ink jetting;

etching the conductive film by using the resist pattern as a mask toform a conductive pillar on the conductive pattern;

forming an insulating film over the substrate so as to cover theconductive pillar and first wiring;

etching back the insulating film to expose an upper surface of theconductive pillar; and

forming a second wiring on the insulating film wherein the second wiringcontacts the upper surface of the conductive pillar so that the firstwiring is electrically connected to the second wiring through theconductive pillar.

As described above, according to the present invention in which aconductive layer is fondled by ink jetting, a pixel electrode, a lightemitting layer, an opposite electrode of a light emitting element, forexample, can be formed sequentially without being exposed to the air, byexchanging composition to be jetted (discharged) from an ink head, or anink head that is filled with composition.

The present invention using an ink jetting method has advantageouseffects such as superiority in evenness of a film thickness, as comparedwith a screen printing method by which a thin film (typically, a lightemitting layer) is formed by applying liquid solution, and baking byusing a print roll or a relief board on which a pattern to be printed isengraved.

According to the present invention having the above describedstructures, wirings or a conductive layer can be easily formed over alarge size substrate of which side exceeds 1.0 m. An unnecessarymaterial is not produced so much, since a required amount of a materialmay be applied to a desired portion. Therefore, the usability of thematerial is enhanced and the manufacturing cost can be cut down.

The steps such as light-exposure and developing can be drasticallyreduced because a mask is not required. For example, a plurality of thinfilms such as a light emitting layer and electrodes of a light emittingelement, for example, can be formed sequentially by exchangingcomposition to be jetted from an ink head, or an ink head that is filledwith composition. Consequently, the throughput and productivity can beimproved. Further, a mask for light-exposure is not necessary, and thus,circuit wirings that are inputted into a personal computer can bemanufactured immediately.

These and other objects, features and advantages of the presentinvention become more apparent upon reading of the following detaileddescription along with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a cross sectional view showing a liquid crystal panel inaccordance with one embodiment of the present invention;

FIGS. 2A to 2D are cross sectional views showing a method formanufacturing a liquid crystal panel according to the present invention;

FIGS. 3A to 3C are cross sectional views showing a method formanufacturing a liquid crystal panel according to the present invention;

FIGS. 4A to 4D are cross sectional views showing a method formanufacturing an EL panel according to the present invention;

FIGS. 5A to 5D are cross sectional views showing a method formanufacturing an EL panel according to the present invention;

FIGS. 6A to 6C are cross sectional views showing a method formanufacturing an EL panel according to the present invention; and

FIG. 7 is a perspective view showing a manufacturing method of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION Embodiment Mode

In an embodiment mode of the present invention, a manufacturing step isdescribed by using an active matrix liquid crystal display device as anexample with reference to FIGS. 1 and 7.

First, an active matrix substrate is formed by using a substrate 101that is transparent to light. The substrate with such a large area as600 mm×720 mm, 680 mm×880 mm, 1000 mm×1200 mm, 1100 mm×1250 mm, 1150mm×1300 mm, 1500 mm×1800 mm, 1800 mm×2000 mm, 2000 mm×2100 mm, 2200mm×2600 mm, or 2600 mm×3100 mm may be preferably used for reducing amanufacturing cost. A substrate made of barium borosilicate glass,aluminoborosilicate glass, or the like, as typified by #7059 glass or#1737 glass produced by Corning Inc. can be used. In addition, atransparent substrate such as a quartz substrate or a plastic substratecan be used alternatively.

At first, as shown in FIG. 1, a base film 102 made of an insulating filmis formed on the substrate 101 in this embodiment mode. A semiconductorlayer 103 is formed over the base film 102. The semiconductor layer 103is formed to be from 25 nm to 80 nm thick by a publicly known method(sputtering, LP CVD, plasma CVD or the like). In this embodiment mode,an amorphous silicon film of 50 nm in thickness is formed by plasma CVD.Subsequently, laser crystallization by an excimer laser is performedadditionally to enhance the crystallinity. Doping (channel doping) of avery small amount of an impurity element (boron) may be performed tocontrol the threshold value of a TFT after forming the semiconductorlayer. After that, a resist is patterned by ink jetting. Thesemiconductor layer 103 is fowled by dry etching by using the resist asa mask.

Then, a gate insulating film 105 for covering the semiconductor layer103 is formed. The gate insulating film 105 is formed from an insulatingfilm including silicon by plasma CVD or sputtering to have a thicknessof from 40 nm to 150 nm. In this embodiment mode, a silicon oxynitridefilm is formed to have a thickness of 115 nm by plasma CVD as the gateinsulating film (and a capacitor insulating film) 105.

Subsequently, a first conductive layer (a gate wiring, a gate electrode,a capacitor electrode) 106 is formed by ink jetting under reducedpressure or in vacuum. A perspective view of this state is shown in FIG.7.

In FIG. 7, reference numeral 401 denotes a substrate, 402 denotes ahorizontal scanning driver circuit, 403 denotes a vertical scanningdriver circuit, and 404 denotes ink head. A solution is applied by usingone or plural ink heads 404 and scanning in parallel with the surface ofthe substrate 401 from side to side and up and down. According to thestructure, wirings can be applied to only a desired portion.

Although the ink head having three nozzles is shown in FIG. 7, an inkhead having one nozzle may be used. A plurality of ink heads each havinga different nozzle diameter may be provided, and used appropriatelydepending on the application. Generally, an ink head has a nozzlediameter of from 50 μm to 100 μm. Although the throughput depends on thenozzle diameter, a plurality of nozzles may be arranged in parallel soas to have the same length as that of one row or one column to form byscanning once in consideration of the throughput. Alternatively, anarbitrary number of nozzles may be provided to scan plural times andplural times of scanning may be performed on the same portion forrecoating. Further, the ink head 404 is preferably scanned, but thesubstrate 401 may be moved instead. The distance between the substrate401 and the ink head 404 is preferably as short as possible so as todrop on a desired portion, specifically, appropriately from 0.1 mm to2.0 mm.

The amount of the composition jetted (discharged) once from the ink headis preferably from 10 pl to 70 pl, the viscosity is preferably 100 cp orless, the grain size is preferably 0.1 μm or less. This prevents drying.Also, if the viscosity is too high, the composition may not be smoothlydischarged from the ink head. Thus, the viscosity of the composition,the surface tension, and the drying rate are properly adjusted inaccordance with the solvent to be used and the purpose. The compositiondischarged from the ink head is preferably formed in a linear shape or astripe shape by subsequently dropping the composition on the substrate.However, the composition may be dropped onto the predetermined spots,per dot, for example.

As the composition jetted from an ink head, the one in which aconductive material that is properly selected from tantalum (Ta),tungsten (W), titanium (Ti), molybdenum (Mo), aluminum (Al), copper(Cu), chromium (Cr), or neodymium (Nd), an alloy material of the metal,a compound material mainly containing the metal and a AgPdCu alloy, isdissolved and dispersed in a solvent can be used. As the solvent, anorganic solvent, for example, ester such as butyl acetate or ethylacetate, alcohols such as isopropyl alcohol or ethyl alcohol, methylethyl ketone, or acetone, is used. The concentration of the solvent isproperly determined according to the types of the conductive materials.

Ultra fine particles (nanometal grains) in which silver (Ag), gold (Au),or platinum (Pt) is dispersed into a solvent with a grain size of 10 nmor less may be used for the composition jetted from the ink head. Theproblem of the nozzle blocking can be solved by using the composition inwhich fine grains in a grain size are dispersed or dissolved in thesolvent. The grain size of the constituent material of the compositionis required to be smaller than the diameter of the nozzle in the presentinvention using an ink jetting method. Further, a conductive polymersuch as polyethylene dioxythiophene/polystyrenesulfonic acid (PEDT/PSS)solution may be used instead.

The wiring resistance can be lowered when a low resistance metal such assilver or copper is used as a wiring material; thus, such a lowresistance metal is preferably used when a large size substrate is used.Moreover, since these metal materials are difficult to process by aconventional dry etching method, it is extremely effective thatpatterning is directly performed thereon by ink jetting. However, in thecase of using copper, a conductive film having a barrier function, whichcan prevent the diffusion of copper, is preferably provided so as not tohave an adverse affect on the electric characteristic of a transistor. Awiring can be formed, without diffusing copper into the semiconductorincluded in a transistor by the conductive film having a barrierfunction. As the conductive film having a barrier function, one kind ofor plural kinds of laminated films selected from tantalum nitride (TaN),titanium nitride (TiN), or tungsten nitride (WN) can be used. An oxidantinhibitor is preferably used at the same time since copper is easilyoxidized.

Thereafter, the solvent is volatilized to enhance the density of thecomposition and reduce the resistance value by performing a heattreatment on the substrate over which the first conductive layer isformed within the range of from 150° C. to 300° C. in the normalpressure, under a reduced pressure, or in a vacuum. The solvent in thecomposition discharged from the ink head 404 is preferably the one whichvolatilizes after dropping the composition on the substrate. When thesolvent having higher volatility such as toluene is used, the solvent isvolatilized after dropping the composition on the substrate. In thatcase, the heat treatment step may be omitted. However, the solvent ofthe composition is not particularly limited, and in the case of usingthe solvent which volatilizes after the dropping, the density of thecomposition may be enhanced and the resistance value may be reduced byperforming a heat treatment. The heat treatment may be performed, everytime a thin film is formed by ink jetting, every optional step, or afterfinishing the whole steps.

A lamp annealing apparatus in which the substrate is directly andrapidly heated by using a lamp such as a halogen lamp as a heat sourceor a laser irradiation apparatus in which the substrate is irradiatedwith laser light is used for the heat treatment. A heat treatment can beperformed only on the desired portion by scanning the heat source itselfin the both apparatuses. As the other methods, an annealing furnacewhich is set at predetermined temperature may be used. When a lamp isused; light having a wavelength which dose not destroy the compositionof the thin film to be heat-treated and which is capable of onlyheating, for example, light having a longer wavelength than 400 nm,namely, light having the longer wavelength than that of the infraredlight is preferably used. In consideration of the handling, afar-infrared ray (the typical wavelength is from 4.0 μm to 25 μm) ispreferably used. When laser light is used, the beam spot on thesubstrate of the laser light emitted from the laser oscillator ispreferably formed to have a linear shape so as to have the same lengthas that of the row or column of the substrate. And the laser irradiationcan be finished by scanning once. In the embodiment mode, the substrateis irradiated with laser light having a beam spot having a linear shapeas the heat treatment.

Subsequently, an impurity element imparting a conductive type of n-typeor p-type is doped into the semiconductor layer 103 by using the gateelectrode 106 as a mask. At the same time, a region which is not dopedwith any impurity elements or doped with a small amount of impurityelements (which is generically referred to as a channel formationregion) is formed. Further, a portion of the gate insulating film isetched and removed by using the first conductive layer 106 as a mask,thereby exposing the surface of the semiconductor layer 103 in theimpurity region.

Thereafter, as shown in Embodiments 1 and 2, a conductive film such asan Al film with a thickness of 1.5 μm is deposited over the entiresurface once, and a resist pattern is formed on a desired particularregion of the conductive film by ink jetting, and then, pillars 108 and109 made of Al are formed by anisotropic dry etching. A first interlayerinsulating film 110 made of an insulating film is formed. A siliconoxynitride film is formed to be 100 nm thick by plasma CVD as the firstinterlayer insulating film 110. Then, a second interlayer insulatingfilm 111 is formed over the first interlayer insulating film 110. Atransparent acrylic film may be formed to be 1.6 μm thick over theentire surface by spin coating as the second interlayer insulating film111. A silicon nitride film is formed to be 50 nm thick as a thirdinterlayer insulating film 112. It should be noted that the interlayerinsulating films are not limited to the above described materials.

The third interlayer insulating film (such as silicon nitride film) 112,the second interlayer insulating film (such as acrylic film) 111, andthe first interlayer insulating film (such as a silicon oxynitride film)110 are sequentially etched back, thereby exposing top portions of thepillars 108 and 109.

After that, second conductive layers (source wiring, drain wiring) maybe formed to be in contact with the conductor pillar 108 and 109 by inkjetting. (not shown) It is required to set the viscosity of compositionto be jetted to an optimum value.

Then, a pixel electrode 115 made of a transparent conductor is formedover the entire surface so that it is electrically connected to theconductor pillar (or, the second conductive layer in the case of formingthe second conductive layer). As an example of the pixel electrode 115,a compound of indium oxide and tin oxide (ITO), a compound of indiumoxide and zinc oxide, zinc oxide, tin oxide, indium oxide, titaniumnitride and the like can be given. In this embodiment mode, an ITO filmis formed to have a thickness of 0.1 μm by ink jetting as the pixelelectrode 115.

As described above, an active matrix substrate comprising a pixelportion that has a source wiring, a TFT of the pixel portion and astorage capacitor, and a terminal portion can be manufactured.

An orientation film 137 is formed over the active matrix substrate and arubbing treatment is performed thereto. In this embodiment mode, beforeforming the orientation film 137, a columnar spacer 116 for keeping thesubstrate interval is formed in the desired position by patterning anorganic resin film such as an acrylic resin film. Instead of thecolumnar spacer, a spherical spacer may be applied to the whole surfaceof the substrate.

An opposite substrate is prepared. The opposite substrate is providedwith a color filter 134 in which a colored layer and a light-shieldinglayer (not shown) are arranged in accordance with each pixel. Inaddition, a planarization film is provided so as to cover the colorfilter and the light-shielding layer. Then, an opposite electrode 1370formed of a transparent conductive film is formed over the planarizationfilm so as to overlap with the pixel portion. The orientation film 136is formed over the whole surface of the opposite substrate, and arubbing treatment is performed thereto.

After applying a sealant so as to surround the pixel portion of theactive matrix substrate, a liquid crystal 140 is jetted over the regionsurrounded by the sealant under reduced pressure by ink jetting. Theactive matrix substrate and the opposite substrate are bonded with thesealant 121 under reduced pressure without being exposed to the air. Afiller (not shown) is mixed into the sealant 121. Therefore, the twosubstrates are bonded with an even interval by the filler and thecolumnar spacer 116. According to the method that the liquid crystal isjetted by ink jetting, the amount of the liquid crystal used in themanufacturing steps can be reduced, and the cost required in the case ofusing a large size substrate can be widely reduced.

Thereupon, in this embodiment mode, the substrate is bonded to theopposite substrate provided with the sealant after the liquid crystalmaterial is jetted (or dropped) only over the pixel electrode that areformed over the substrate by ink jetting, that is, over the pixelportion. Both of applying the sealant and dropping of the liquid crystalmay be performed on the opposite substrate or on the substrate providedwith the pixel portion.

A piezo system that is applied for ink-jet printers may be employed foran ink jetting method since controllability of an ink drop is higher andthe kind of an ink can be selected freely. Note that, the piezo systemhas two types: a MLP (Multi Layer Piezo) type and a ML Chip (Multi LayerCeramic Hyper Integrated Piezo Segments).

In this embodiment mode, a liquid crystal display device can bemanufactured by discharging (or dropping) plural drops of a small amountof liquid crystal toward a pixel electrode. By employing an ink jettingmethod, the small amount of the liquid crystal can be freely adjusted bythe number of jetting and the number of the jetting point.

Thus, an active matrix liquid crystal display device can bemanufactured. Note that, if necessary, the active matrix substrate orthe opposite substrate is sectioned to have a desired shape. Further, anoptical film such as a polarizing plate 117 is provided appropriately byusing known techniques. An FPC is further bonded by using knowntechniques.

A liquid crystal module obtained according to the above steps isprovided with a backlight 120 and an optical waveguide 119. The activematrix liquid crystal device (transmissive type) is completed bycovering the liquid crystal module with a cover 122. A part of the crosssection thereof is shown in FIG. 1. Note that, the cover and the liquidcrystal module are fixed with an adhesive or an organic resin. Thepolarizing plate 117 is bonded to the both of the active matrixsubstrate and the opposite substrate, since the liquid crystal displaydevice is a transmissive type.

Further, an example of the transmissive type is shown in this embodimentmode; however, the present invention is not limited thereto, and areflective or semi-transparent liquid crystal display device can also bemanufactured according to the present invention. When a reflectiveliquid crystal display device is obtained, a metal film with highreflectance, typically, a material film containing aluminum or silvermainly, or a lamination thereof may be used for a pixel electrode.

There are mainly two types of liquid crystal display devices: a passivetype (simple matrix type) and an active type (active matrix type); thepresent invention can be applied to the either of the types.

This embodiment mode is not limited to the above described examples, andcan be applied to various applications unless it departs from the scopeof the present invention.

Embodiment 1

Embodiment 1 of the present invention is described in detail withreference to FIGS. 2A to 2D and FIGS. 3A to 3C. In the presentinvention, a liquid crystal display device is manufactured by apatterning treatment using an ink jetting method, without performing aconventional patterning treatment using a photolithography method. Notethat, the present invention is not limited to the following description,since it is to be understood that various changes and modifications willbe apparent to those skilled in the art, unless such changes andmodifications depart from the scope and purpose of the presentinvention. Therefore, the present invention should not be limited to theembodiment to be described hereinafter. Note that, in structures to bedescribed hereinafter of the present invention, the same referencenumeral for showing the same elements are used commonly in the figures.Hereinafter, a step of manufacturing an n-channel TFT (for switching)and a capacitor over the same substrate is described, according to thepresent invention.

A flexible substrate typified by a glass substrate and a plasticsubstrate, or the like, which can withstand the processing temperatureof the steps, is used for a substrate 201 (FIG. 3A). In this embodiment,a glass substrate is used. A base film 202 made of an insulating film isformed on the substrate 201. The base film 202 may be either of a singlelayer or laminated layers. In this embodiment, the base film has atwo-layer structure. A silicon nitride oxide film with the filmthickness of 50 nm is formed for a first layer and a silicon oxynitridefilm with the film thickness of 50 nm is formed for the second layer bysputtering for the two-layer structure of the base film. Then thesurface is flattened by CMP, or the like (FIG. 2A).

Subsequently, a semiconductor layer 203 is formed over the base film202. As the semiconductor layer 203, a semiconductor film is formed witha thickness of from 25 nm to 80 nm by a known method (such assputtering, LPCVD, plasma CVD).

Then, the semiconductor film is crystallized by a known crystallizationmethod (laser crystallization, RTA thermal crystallization usingannealing furnace, thermal crystallization using a metal element thatpromotes crystallization, or the like). Then, the obtained crystallinesemiconductor film is patterned into a desired shape to form thesemiconductor layer 203. Note that, an amorphous semiconductor film, amicrocrystalline semiconductor film, a crystalline semiconductor film, acompound semiconductor film with an amorphous structure such as anamorphous silicon germanium film, or the like may be used as thesemiconductor film.

In this embodiment, a 50-nm-thick amorphous silicon film is formed byplasma CVD. Then, a solution containing nickel is applied and held overthe amorphous silicon film, dehydrogenation (500° C. for 1 hour) isperformed on the amorphous silicon film, and then, thermalcrystallization (550° C., 4 hours) is conducted thereto, thereby forminga crystalline silicon film. Thereafter, a resist 205, which isdischarged from an ink jet nozzle 204 by ink jetting, is exposed topattering, and the semiconductor layer 203 is formed by dry etchingusing the resist pattern as a mask (FIG. 2B).

Note that, a continuous wave or pulsed gas laser or solid-state lasermay be employed, as a laser used in the case where the crystallinesemiconductor film is formed by laser crystallization. As the former gaslaser, an excimer laser or the like is used. Also, as the lattersolid-state laser, a laser which uses crystals such as YAG, YVO₄, or thelike which is doped with Cr, Nd or the like is used. Note that, incrystallization of the amorphous semiconductor film, it is preferablethat the solid-state laser capable of continuously oscillating be usedand that the oscillation of any one of the second harmonic wave throughthe fourth harmonic wave with respect to the fundamental wave be appliedin order to obtain crystals with a large grain size. In the case ofusing the above lasers, the laser beam emitted from a laser oscillatoris condensed in a linear shape by an optical system, and thesemiconductor film is preferably irradiated with the laser beam.

However, in this embodiment, since the crystallization of the amorphoussilicon film is conducted by using a metal element that promotescrystallization, the metal element remains in the crystalline siliconfilm. Therefore, an amorphous silicon film with a thickness of from 50nm to 100 nm is formed over the crystalline silicon film, and a heattreatment (such as RTA or thermal annealing using an annealing furnace)is performed thereon to diffuse the metal element into the amorphoussilicon film. After the heat treatment, the amorphous silicon film isremoved by etching. As a result, the metal element content of thecrystalline silicon film can be reduced or eliminated. After forming thesemiconductor layer 203, a minute amount of impurity elements (boron)may be doped (channel doping) in order to control the threshold value ofa TFT.

Then, a gate insulating film 206 for covering the semiconductor layer203 is formed. The gate insulating film 206 is formed of an insulatingfilm including silicon by plasma CVD or sputtering to have a thicknessof from 40 nm to 150 nm. In this embodiment, a silicon oxynitride filmis formed to have a thickness of 115 nm by plasma CVD as the gateinsulating film.

Subsequently, the first conductive layer (a gate wiring, a gateelectrode, a capacitor electrode) 207 is formed by ink jetting underreduced pressure or in vacuum (FIG. 2C). A perspective view of thisstage is shown in FIG. 7.

In FIG. 7, reference numeral 401 denotes a substrate, 402 denotes ahorizontal scanning driver circuit, 403 denotes a vertical scanningdriver circuit, and 404 denotes an ink head(s). Solution is applied byusing one or plural ink heads 404 and scanning in parallel with thesurface of the substrate 401 from side to side and up and down.According to the structure, wirings can be applied to only a desiredportion.

Although the ink head having three nozzles is shown in FIG. 7, an inkhead having one nozzle may be used. A plurality of ink heads each havingdifferent nozzle diameter are provided, and used appropriately dependingon the application. Generally, an ink head has a nozzle diameter of from50 μm to 100 μm. Although the throughput depends on the nozzle diameter,a plurality of nozzles may be arranged in parallel so as to have thesame length as that of one row or one column to form by scanning once inconsideration of the throughput. Alternatively, an arbitrary number ofnozzles may be provided to scan plural times and plural times ofscanning may be performed on the same portion for recoating. Further,the ink head 404 is preferably scanned, but the substrate 401 may bemoved instead. The distance between the substrate 401 and the ink head404 is preferably as short as possible so as to drop on a desiredportion, specifically, appropriately from 0.1 mm to 2.0 mm.

Preferably, the amount of composition jetted once from the ink head ispreferably from 10 pl to 70 pl, the viscosity is preferably 100 cp orless, the grain size is preferably 0.1 μm or less. This is because theviscosity is too high to apply the composition smoothly from the inkhead. And the above conditions can prevent drying out. Thus, theviscosity of the composition, the surface tension, and the drying rateare properly adjusted in accordance with the solvent to be used and thepurpose. The composition discharged from the ink head is preferablyformed in a linear shape or a stripe shape by subsequently dropping thecomposition on the substrate. However, the composition may be droppedonto the predetermined spots, per dot, for example.

As the composition jetted from an ink head, the one in which aconductive material that is properly chosen from an element selectedfrom tantalum (Ta), tungsten (W), titanium (Ti), molybdenum (Mo),aluminum (Al), copper (Cu), chromium (Cr), or neodymium (Nd), an alloymaterial or compound material mainly containing the above element, or aAgPdCu alloy, is dissolved and dispersed in a solvent can be used. Asthe solvent, an organic solvent, for example, ester such as butylacetate, or ethyl acetate, alcohols such as isopropyl alcohol or ethylalcohol, methyl ethyl ketone, or acetone, is used. The concentration ofthe solvent is properly determined according to the types of theconductive materials.

Ultra fine particles (nanometal grains) in which silver (Ag), gold (Au),or platinum (Pt) is dispersed into a solvent with a grain size of atmost 10 nm may be used for the composition jetted form the ink head. Theproblem of the nozzle blocking may be solved by using the composition inwhich fine grains in grain size are dispersed or dissolved in thesolvent. The grain size of the constituent material of the compositionis required to be smaller than the diameter of the nozzle in the presentinvention using an ink jetting method. Further, a conductive polymersuch as polyethylene dioxythiophene/polystyrenesulfonic acid (PEDT/PSS)solution may be used instead.

The wiring resistance can be lowered when a low resistance metal such assilver or copper is used as a wiring material; thus, such a lowresistance metal is preferably used when a large size substrate is used.Moreover, since these metal materials are difficult to process by aconventional dry etching method, it is extremely effective thatpatterning is directly performed thereon by ink jetting. However, in thecase of using copper, a conductive film having a barrier function, whichcan hinder diffusion of the copper, is preferably provided so as not tohave an adverse affect on the electric characteristic of a transistor. Awiring can be formed, without diffusing copper into the semiconductorincluded in a transistor by the conductive film having a barrierfunction. As the conductive film having a barrier function, one kind ofor plural kinds of laminated films selected from tantalum nitride (TaN),titanium nitride (TiN), or tungsten nitride (WN) can be used. An oxidantinhibitor is preferably used at the same time since copper is easilyoxidized.

Thereafter, the solvent is volatilized to enhance the density of thecomposition and reduce the resistance value by performing a heattreatment on the substrate over which the first conductive layer isformed within the range of from 150° C. to 300° C. in normal pressure,under reduced pressure, or in vacuum. The solvent in the compositionjetted from the ink head 204 is preferably the one which volatilizesafter dropping the composition on the substrate. When the solvent havinghigher volatility such as toluene is used, the solvent is volatilizedafter dropping the composition on the substrate. In that case, the heattreatment step may be omitted. However, the solvent of the compositionis not particularly limited, and in the case of using the solvent whichvolatilizes after the dropping, the density of the composition may beenhanced and the resistance value may be reduced by performing a heattreatment. The heat treatment may be performed every time a thin film isformed by ink jetting or every optional step; or after finishing thewhole steps.

A lamp annealing apparatus in which the substrate is directly andrapidly heated by using a lamp such as a halogen lamp as a heat sourceor a laser irradiation apparatus in which the substrate is irradiatedwith a laser light is used for the heat treatment. A heat treatment canbe performed only on the desired portion by scanning the heat sourceitself in the both apparatuses. As the other methods, an annealingfurnace which is set at predetermined temperature may be used. When alamp is used, light having a wavelength which dose not destroy thecomposition of the thin film to be heat-treated and which is capable ofonly heating, for example, light having a longer wavelength than 400 nm,namely, light having the longer wavelength than that of the infraredlight is preferably used. In consideration of the handling, afar-infrared ray (the typical wavelength is from 4.0 μm to 25 μm) ispreferably used. When laser light is used, the beam spot on thesubstrate of the laser light emitted from the laser oscillator ispreferably formed to have a linear shape so as to have the same lengthas that of the row or column of the substrate. And the laser irradiationcan be finished by scanning once. In this embodiment, the substrate isirradiated with a laser light having a beam spot of a linear shape asthe heat treatment.

Subsequently, an impurity element imparting a conductive type of n-typeor p-type is doped into the semiconductor layer 203 by using the gateelectrode 207 as a mask. In this embodiment, an impurity elementimparting n-type is added into the semiconductor layer 203, or animpurity element imparting p-type is added into the semiconductor layer203, thereby forming an impurity region. At the same time, a regionwhich is not doped with any impurity elements or doped with a smallamount of impurity elements (which is generally called as a channelformation region) is formed. Further, a portion of the gate insulatingfilm is etched and removed by using the gate electrode 205 as a mask,thereby exposing the surface of the semiconductor layer in the impurityregion (FIG. 2C).

Thereafter, a thick conductive film 208 is deposited once, and a resistpattern 209 is formed on a particular portion of the conductive film byink jetting. For the conductive film, a metal such as Al, Ti, or TiN,carbon, an organic material having conductivity or the like can be alsoused appropriately. Alternatively, for the material of the resistpattern 209, a metal material, an inorganic material such as SiO₂ can beused instead of a conventional organic material. In particular, when themetal material is used, it is unnecessary to remove the metal elementafter processing a pillar to be described below. A metal material havingselectivity in etching processing of pillar can be used for the metalmaterial. For example, a noble metal such as Au, Ag, Cu, or Pt which canbe hard to be etched by dry etching can be also used (FIG. 2D).

Subsequently, a conductor pillar 210 is formed by anisotropic dryetching with the resist pattern 209 as a mask. A first interlayerinsulating film 211 made of an insulating film is formed. The firstinterlayer insulating film 211 is formed from an insulating filmincluding silicon to be from 50 nm to 200 nm thick by plasma CVD orsputtering. In this embodiment, a 100-nm-thick silicon oxynitride filmis formed as the first interlayer insulating film 211 by plasma CVD.

Then, a second interlayer insulating film 212 is formed over the firstinterlayer insulating film 211. A silicon oxide film formed by CVD, asilicon oxide film applied by a SOG (Spin On Glass) method or spincoating, an organic insulating film such as acrylic or anon-photosensitive organic insulating film, each of which is from 0.7 μmto 5.0 μm thick, is used for the second interlayer insulating film 212.An acrylic film of 1.6 μm thick is formed by CVD in this embodiment. Itis noted that the second interlayer insulating film 212 is provided forthe sake of smoothing unevenness due to a TFT formed over the substrate200 and leveling the surface, and thus, a film having a levelingproperty is favorable. Further, a silicon nitride film is formed to be0.1 μm thick as a third interlayer insulating film 213.

The third interlayer insulating film (such as silicon nitride film) 213,the second interlayer insulating film (such as acrylic film) 212, andthe first interlayer insulating film (such as a silicon oxide film) 211are sequentially etched back, thereby exposing a top portion of theconductor pillar 210. After that, the second conductive layer (sourcewiring, drain wiring) 214 is formed to be in contact with the conductorpillar 210 by ink jetting. FIG. 3A shows a cross sectional view of thestate.

The second conductive layer is formed to be a single layer or a laminateby using the composition in which a conductive material is dissolved ordispersed in a solution as the composition jetted from the ink head,like the first conductive layer. In the case of forming the secondconductive layer, it is necessary that the viscosity of the compositionto be jetted should be set to a suitable value. In this embodiment, asecond conductive layer 214 has a two layer structure, in which a firstlayer is made of titanium and a second layer is made of silver. Then, aheat treatment is performed. A transistor is formed over the substrate201 having an insulating surface according to the above described steps.

Then, a pixel electrode 215 made of a transparent conductor is formedover the entire surface so that it is electrically connected to thesecond conductive layer 214 (FIG. 3B). As an example of the pixelelectrode 215, a compound of indium oxide and tin oxide (ITO), acompound of indium oxide and zinc oxide, zinc oxide, tin oxide, indiumoxide, titanium nitride and the like can be given. In this embodiment,an ITO film is formed to have a thickness of 0.1 μm by ink jetting asthe pixel electrode 215 (FIG. 3B).

As described above, an active matrix substrate comprising a pixelportion that has a source wiring, a TFT of the pixel portion and astorage capacitor, and a terminal portion can be manufactured.

After that, an opposite substrate 219 where a common electrode 216, acolor filter 217, a black matrix 218, and the like have been formed, isbonded. Then, a liquid crystal 220 is injected by a predetermined methodto complete a liquid crystal display device (FIG. 3C). Note that, stepsof equipping back light and the like are omitted here.

As described above, Embodiment 1 of the present invention is describedabout an active matrix liquid crystal display device. However, thepresent invention is not limited to this embodiment and can similarly beapplied based on the scope of the present invention. For example, thepresent invention can be applied to an active matrix organic EL displaydevice, as shown in Embodiment 2. The materials or the formation stepsdescribed in this embodiment can be used appropriately and selectivelyin accordance with the scope of the present invention.

Embodiment 2

Embodiment 2 of the present invention is described in detail withreference to FIGS. 4A to 4D, FIGS. 5A to 5D and FIGS. 6A to 6C. In thepresent invention, an EL display device is manufactured by a patterningtreatment using an ink jetting method, without performing a conventionalpatterning treatment using a photolithography method. Note that, thepresent invention is not limited to the following description, since itis to be understood that various changes and modifications will beapparent to those skilled in the art, unless such changes andmodifications depart from the scope and purpose of the presentinvention. Therefore, the present invention should not be limited to theembodiment to be described hereinafter. Note that, in structures of thepresent invention, the same reference numeral for showing the sameelements are used commonly in the figures. Hereinafter, a manufacturingstep of an EL display device where an n-channel TFT (for switching) andtwo p-channel TFTs (for driving) are formed on the same substrate,according to the present invention, is described.

A flexible substrate typified by a glass substrate and a plasticsubstrate, or the like, which can withstand the processing temperatureof the steps, is used for a substrate 301 (FIG. 2A). In this embodiment,a glass substrate is used. A base film 302 made of an insulating film isformed on the substrate 301. The base film 302 may be either of a singlelayer or laminated layers. In this embodiment, the base film has atwo-layer structure. A silicon nitride oxide film with the filmthickness of 50 nm is formed for a first layer and a silicon oxynitridefilm with the film thickness of 50 nm is formed for a second layer bysputtering for the two-layer structure of the base film. Then thesurface is flattened by CMP, or the like (FIG. 4A).

Subsequently, a semiconductor layer 303 is formed over the base film302. As the semiconductor layer 303, a semiconductor film is formed witha thickness of from 25 nm to 80 nm by a known method (such assputtering, LPCVD, plasma CVD). Then, the semiconductor film iscrystallized by a known crystallization method (laser crystallization,RTA, thermal crystallization using an annealing furnace, thermalcrystallization using a metal element that promotes crystallization, orthe like). Then, the obtained crystalline semiconductor film ispatterned into a desired shape to form the semiconductor layer 303. Notethat, an amorphous semiconductor film, a microcrystalline semiconductorfilm, a crystalline semiconductor film, a compound semiconductor filmwith an amorphous structure such as an amorphous silicon germanium film,or the like may be used as the semiconductor film.

As in Embodiment 1, a 50-nm-thick amorphous silicon film is formed byusing plasma CVD. Then, a solution containing nickel is applied and heldover the amorphous silicon film, dehydrogenation (500° C. for 1 hour) isperformed on the amorphous silicon film, and then, thermalcrystallization (550° C., 4 hours) is conducted thereon, thereby forminga crystalline silicon film. Thereafter, a resist 305, which isdischarged from an ink jet nozzle 304 by ink jetting, is exposed topattering, and the semiconductor layer 303 is formed by dry etching byusing the resist pattern as a mask (FIG. 4B).

Thereafter, a gate insulating film 306 is formed. A silicon oxynitridefilm is formed to be 115 nm thick by plasma CVD as the gate insulatingfilm 306 (FIG. 4C).

A first conductive layer (gate wirings, a gate electrode) 307 is formedunder reduced pressure or in vacuum by ink jetting (FIG. 4D).

Thereafter, the solvent is volatilized to obtain favorable electricconductive properties by performing a heat treatment on the substrateover which the first conductive layer is formed within the range of from150° C. to 300° C. in normal pressure, under reduced pressure, or invacuum. The solvent in the composition jetted from the ink head nozzle304 is preferably the one which volatilizes after dropping thecomposition on the substrate. When the solvent having higher volatilitysuch as toluene is used, the solvent is volatilized after dropping thecomposition on the substrate. In that case, the heat treatment step maybe omitted. However, the solvent of the composition is not particularlylimited, and in the case of using the solvent which volatilizes afterthe dropping, the viscosity of the composition may be reduced to obtainthe desired viscosity value by performing a heat treatment. The heattreatment may be performed every time a thin film is formed by inkjetting or every optional step, or after finishing the whole steps.

Subsequently, an impurity element imparting a conductive type of n-typeor p-type is doped into the semiconductor layer 303 by using the gateelectrode 307 as a mask. In this embodiment, an impurity elementimparting n-type is added into the semiconductor layer 303, or animpurity element imparting p-type is added into the semiconductor layer303, thereby forming an impurity region. At the same time, a regionwhich is not doped with any impurity elements or doped with a smallamount of impurity elements (which is generically named as channelformation region) is formed.

Further, a portion of the gate insulating film is etched and removed byusing the gate electrode 307 as a mask, thereby exposing the surface ofthe semiconductor layer 303 in the impurity region.

Thereafter, a thick conductive film 308 is deposited once, and a resistpattern 309 is formed on a desired particular portion of the conductivefilm 308 by ink jetting. For the conductive film 308, a metal such asAl, Ti, or TiN, carbon, an organic material having conductivity or thelike can be also used appropriately.

Subsequently, a pillar 310 is formed by anisotropic dry etching by usingthe resist pattern 309 as a mask. A first interlayer insulating film 311made of an insulating film is formed. The first interlayer insulatingfilm 311 is formed from an insulating film including silicon to be from50 nm to 200 nm thick by plasma CVD or sputtering. In this embodiment, a100-nm-thick silicon oxynitride film is formed by plasma CVD.

Then, a second interlayer insulating film 312 is formed over the firstinterlayer insulating film (a silicon oxynitride film) 311. A siliconoxide film formed by CVD, a silicon oxide film applied by a SOG (Spin OnGlass) method or spin coating, an organic insulating film such asacrylic or a non-photosensitive organic insulating film, each of whichis from 0.7 μm to 5.0 μm thick, may be used for the second interlayerinsulating film 312. An acrylic film of 1.6 μm thick is formed by CVD inthis embodiment. It is noted that the second interlayer insulating film312 is provided for the sake of smoothing unevenness due to a TFT formedover the substrate 301 and leveling the surface, and thus, a film havinga leveling property is favorable (FIG. 5B).

The first to third interlayer insulating films 311, 312 and 315 are eachprovided to obtain a blocking effect for preventing penetration ofoxygen, moisture in the air and various ionic impurities.

The second interlayer insulating film (such as acrylic film) 312, andthe first interlayer insulating film (such as a silicon oxynitride film)311 are sequentially etched back, thereby exposing a top portion of thepillar 310. After that, a second conductive layer (source wiring, drainwiring) 313 is formed to be in contact with the pillar 310 by inkjetting. FIG. 5C shows a cross sectional view of the state.

A second conductive layer 313 is formed to be a single layer or alaminate by using a composition in which a conductive material isdissolved or dispersed in a solution as the composition jetted from theink head, like the first conductive layer. In this embodiment, thesecond conductive layer 312 has a two layer structure, in which a firstlayer is made of titanium and a second layer is made of Cu (copper).Then, a heat treatment is performed.

Thereafter, a thick conductive film is deposited once, and a resistpattern is formed on a desired particular region of the conductive layerby ink jetting. A pillar 314 is formed by anisotropic dry etching byusing the resist pattern as a mask. Similarly, for the conductive film,a metal such as Al, Ti, or TiN, carbon, an organic material havingconductivity or the like can be also used appropriately. Alternatively,for the resist material, a metal material, an inorganic material such asSiO₂ can be used instead of a conventional organic material. Inparticular, when the metal material is used, it is unnecessary to removethe metal element after processing a pillar to be described below. Ametal material having selectivity in etching processing of a pillar canbe used for the metal element. For example, a noble metal such as Au,Ag, Cu, or Pt which can be hard to be etched by dry etching inparticular can be also used, in general.

Then, a third interlayer insulating film 316 is formed over the entiresurface. A silicon nitride film or silicon nitride oxide film of from0.1 μm to 0.2 μm thick is formed by sputtering as the third interlayerinsulating film 316. In this embodiment, a 0.1 μm thick silicon nitridefilm is formed by sputtering as the third interlayer insulating film316. A blocking effect for preventing penetration of oxygen, moisture inthe air and various ionic impurities can be obtained by providing thethird interlayer insulating film 316. Further, a fourth interlayerinsulating film 315 is formed over the entire surface. A silicon oxidefilm formed by CVD, a silicon oxide film applied by a SOG (Spin OnGlass) method or spin coating, an organic insulating film such asacrylic or a non-photosensitive organic insulating film, each of whichis from 0.7 to 5.0 μm thick, is used for the fourth interlayerinsulating film 315. An acrylic film of 1.6 μm thick is formed by spincoating in this embodiment. A film having a good leveling property isfavorable as the fourth interlayer insulating film 315.

The fourth interlayer insulating film (such as acrylic film) 315, andthe third interlayer insulating film (such as a silicon nitride film)316 are sequentially etched back, thereby exposing a top portion of thepillar 314. FIG. 5D shows a cross sectional view of the state.

After that, a third conductive layer (a source wiring, a drain wiring)317 is formed to be in contact with the pillar 314 by ink jetting.

Then, a first pixel electrode 318 made of a transparent conductor isformed over the entire surface so that it is electrically connected towirings for a driving TFT (FIG. 6A). The first pixel electrode 318 ispreferably formed by using a material having a large work function. Asexamples thereof, a compound of indium oxide and tin oxide (ITO), acompound of indium oxide and zinc oxide, zinc oxide, tin oxide, indiumoxide, titanium nitride and the like can be given. In this embodiment,an ITO film is formed to have a thickness of 0.1 μm by ink jetting asthe first pixel electrode 318 (FIG. 6A).

Thereafter, a formation step of light-emitting element of an organic ELis performed. An insulating film is formed to cover an end face of thefirst pixel electrode 318. The material for forming the insulating filmis not limited in particular, and can be formed from an inorganicmaterial or an organic material. Then, a region including an organic ELto be a light emitting layer is formed, at the time, a light emittinglayer 320 is formed to be in contact with the first pixel electrode 318sequentially under reduced pressure or in vacuum (FIG. 6B). The materialfor the light emitting layer 320 is not limited particularly. However,in the case of a full-color display, materials for red, green, blue areeach used. In addition, a second pixel electrode (cathode) 321 is formedby vapor deposition under reduced pressure or in vacuum (FIG. 6C).

The second pixel electrode (cathode) 321 is formed of a laminate of athin film including a metal having a small work function (such aslithium (Li), magnesium (Mg), cesium (Cs)), and a transparent conductivefilm laminated over a thin film including Li, Mg, etc. The filmthickness may be set appropriately so that the second pixel electrodecan serve as a cathode, preferably, about from 0.01 μm to 1.0 μm inthickness. In this embodiment, an alloy film (Al—Li) of aluminum andlithium is formed to be 0.1 μm in thickness. Note that, the second pixelelectrode 321 is formed over the entire surface.

A metal film generally used for a cathode is a metal film that includesan element belonging to Group 1 or 2 in the periodic table. However,since such a metal film is easily oxidized, the surface thereof ispreferably protected. And since the required film thickness is thin, itis preferable that resistance of the cathode is reduced and the cathodeis protected by providing a conductive film having low resistancesupplementarily. A metal film containing aluminum, copper, or silvermainly is used as the conductive film having low resistance.

The light emitting layer 320 and the second pixel electrode 321 can beformed by exchanging composition to be discharged from an ink headnozzle 304, or an ink head nozzle 304 that is filled with composition.At this time, since the steps can be performed without being exposed tothe air, high reliability of the light emitting element that does notresist moisture can be obtained. A heat treatment is performed attemperatures from 150° C. to 300° C. so that the viscosity of the jettedcomposition is set to a desired value (50 cp or less).

A laminate of the first pixel electrode 318, the light emitting layer320 and the second pixel electrode 321 that have been formed in thepreceding steps corresponds to a light emitting element. The first pixelelectrode 318 is an anode and the second electrode 321 is a cathode.There are a singlet excited state and a triplet excited state as anexcited state of the light emitting element, and light emission can beobtained through either of the excited states.

In this embodiment, a case of performing a bottom emission in whichlight generated in the light emitting element passes through thesubstrate 301 side (the bottom side) is shown. However, a top emissionfor transmitting light upwardly from the substrate 301 may be performed.In this case, the first pixel electrode 318 is a cathode and the secondpixel electrode 321 is an anode, and the second pixel electrode 321 maybe formed from a transparent material. Further, a driving TFT ispreferably an n-channel TFT. Note that, the conductivity type of thedriving TFT may be changed appropriately, but a capacitor element isarranged so as to keep voltage between a gate and a source of thedriving TFT. In this embodiment, the display device using a lightemitting element is shown as an example. However, the present inventioncan be applied to a liquid crystal display device using a liquid crystalelement or other display devices.

The present invention having the above structures can be applied to alarger substrate, and can provide a manufacturing method of wirings, aconductive layer and a display device that can enhance the throughput orusability of materials.

Although the present invention has been fully described by way ofEmbodiment Mode and Embodiments with reference to the accompanyingdrawings, it is to be understood that various changes and modificationswill be apparent to those skilled in the art. Therefore, unlessotherwise such changes and modifications depart from the scope of thepresent invention hereinafter defined, they should be constructed asbeing included therein.

1-12. (canceled)
 13. A display device comprising: a substrate; a thinfilm transistor formed over the substrate; an interlayer insulating filmformed over the thin film transistor, the interlayer insulating filmhaving an opening; a conductive pillar in the opening of the interlayerinsulating film wherein the conductive pillar is in electrical contactwith the thin film transistor; a first conductive layer formed over theinterlayer insulating film wherein the first conductive layer is indirect contact with an upper surface of the conductive pillar; and asecond transparent conductive layer formed over the first conductivelayer wherein the second transparent conductive layer is in directcontact with the first conductive layer.
 14. The display deviceaccording to claim 13 wherein the conductive pillar comprises a materialselected from the group consisting of Al, Ti, and TiN.
 15. The displaydevice according to claim 13 wherein the conductive pillar comprises amaterial comprises carbon.
 16. The display device according to claim 13wherein the conductive pillar comprises a conductive organic material.17. The display device according to claim 13 wherein the secondtransparent conductive layer comprises a material selected from thegroup consisting of indium oxide, zinc oxide, and tin oxide.
 18. Adisplay device comprising: a substrate; a thin film transistor formedover the substrate; a first interlayer insulating film formed over thethin film transistor, the first interlayer insulating film having anopening; a first conductive pillar in the opening of the firstinterlayer insulating film wherein the first conductive pillar is inelectrical contact with the thin film transistor; a first conductivelayer comprising copper formed over the first interlayer insulating filmwherein the first conductive layer is in electrical contact with thefirst conductive pillar; a second interlayer insulating film formed overthe first conductive layer, the second interlayer insulating film havingan opening; a second conductive pillar in the opening of the secondinterlayer insulating film; and a pixel electrode formed over the secondinterlayer insulating film wherein the pixel electrode is in directcontact with an upper surface of the second conductive pillar.
 19. Thedisplay device according to claim 18 wherein the first conductive pillarcomprises a material selected from the group consisting of Al, Ti, andTiN.
 20. The display device according to claim 18 wherein the firstconductive pillar comprises a material comprises carbon.
 21. The displaydevice according to claim 18 wherein the first conductive pillarcomprises a conductive organic material.
 22. The display deviceaccording to claim 18 wherein the pixel electrode comprises a materialselected from the group consisting of indium oxide, zinc oxide, and tinoxide.
 23. A display device comprising: a substrate; a thin filmtransistor formed over the substrate; an interlayer insulating filmformed over the thin film transistor, the interlayer insulating filmhaving an opening; a conductive pillar in the opening of the interlayerinsulating film wherein the conductive pillar is in electrical contactwith the thin film transistor; and a conductive layer formed over theinterlayer insulating film wherein the conductive layer is in electricalcontact with the conductive pillar, wherein a size of the opening at aportion close to the substrate is larger than a size of the opening at aportion distant from the substrate.
 24. The display device according toclaim 23 wherein the conductive pillar has a flush upper surface with anupper surface of the interlayer insulating film.
 25. The display deviceaccording to claim 23 wherein the conductive pillar comprises a materialselected from the group consisting of Al, Ti, and TiN.
 26. The displaydevice according to claim 23 wherein the conductive pillar comprises amaterial comprises carbon.
 27. The display device according to claim 23wherein the conductive pillar comprises a conductive organic material.28. The display device according to claim 23 wherein the conductivelayer comprises copper.